The present invention relates generally to an improved vascular graft and method for bridging a defect in a main vessel near one or more branch vessels.
Aneurysms occur in blood vessels in locations where, due to age, disease or genetic predisposition, the blood vessel strength or resiliency is insufficient to enable the blood vessel wall to retain its shape as blood flows therethrough, resulting in a ballooning or stretching of the blood vessel at the limited strength/resiliency location to thereby form an aneurysmal sac. If the aneurysm is left untreated, the blood vessel wall may continue to expand, to the point where the remaining strength of the blood vessel wall is below that necessary to prevent rupture, and the blood vessel will fail at the aneurysm location, often with fatal result.
To prevent rupture, a stent graft of a tubular construction may be introduced into the blood vessel, for example intraluminally. Typically, the stent graft is deployed and secured in a location within the blood vessel such that the stent graft spans the aneurysmal sac. The outer surface of the stent graft, at its opposed ends, is sealed to the interior wall of the blood vessel at a location where the blood vessel wall has not suffered a loss of strength or resiliency. Blood flow in the vessel is thus channeled through the hollow interior of the stent graft, thereby reducing, if not eliminating, any stress on the blood vessel wall at the aneurysmal sac location. Therefore, the risk of rupture of the blood vessel wall at the aneurysmal location is significantly reduced, if not eliminated, and blood can continue to flow through to the downstream blood vessels without interruption.
Although adequate, a stent graft may undesirably become occluded once implanted within an abdominal aorta of a patient to gradually obstruct the lumen of the stent or create thrombosis. Moreover, after implantation of the device, the modulation of haemocompatibility, inflammation or protease activity may undesirably become an issue. The lack of haemocompatabilty may lead to the patient's immune system becoming activated to attack foreign cells and creating blood clots. Additionally, undesirable inflammation causes swelling of the vessels and uncontrollable protease activity may affect the breakdown of clots that form in vessels.